This form of memory involves conscious retrieval of information acquired in a particular place at a particular time ( Tulving, 1983). However, the most pronounced and consistent cognitive deficits in preclinical Alzheimer's disease are seen for tasks assessing episodic memory ( Hodges, 1998 Grober et al., 2000). Preclinical deficits in Alzheimer's disease have been demonstrated in multiple cognitive domains, including psychomotor speed ( Masur et al., 1994), verbal ability and reasoning ( Jacobs et al., 1995) and visuospatial skill (Small et al., 1997). Such findings are vital in characterizing the insidious transition from normal ageing to dementia. Several reports have documented cognitive deficits in persons who will develop Alzheimer's disease prior to diagnostically significant cognitive, behavioural and social changes ( Masur et al., 1994 Jacobs et al., 1995 Small et al., 1997). MANOVA = multivariate analysis of variance, MMSE = Mini-Mental State Examination Introduction the appearance of amyloid plaques and neurofibrillary tangles) accumulate at a relatively slow rate. This may reflect the fact that those biological events that eventually result in clinically diagnosed Alzheimer's disease e.g. The magnitude of these deficits appears to be quite stable, at least up to 3 years before diagnosis. These results indicate that Alzheimer's disease is characterized by a long preclinical period during which episodic memory deficits are detectable. However, there was no evidence for accelerated decline of episodic memory in the incident Alzheimer's disease group from 6 to 3 years before diagnosis. On both preclinical measurement occasions, recall and recognition made independent contributions to group classification in logistic regression analyses. The selective impairment of episodic memory before the diagnosis of Alzheimer's disease is consistent with the view that early changes in the hippocampal complex play an important role in the memory deficit in preclinical Alzheimer's disease. There were no group differences in either forward or backward digit span. The incident Alzheimer's disease cases performed more poorly than their non-demented counterparts both 3 and 6 years before diagnosis on recall and recognition.
Participants were tested on tasks assessing episodic memory free recall and recognition of words) and short-term memory digit span). Using data from a population-based study, we compared persons who developed Alzheimer's disease n = 15) with persons who were non-demented n = 105) 6 and 3 years prior to the diagnosis of dementia.
We sought to determine the course of the preclinical episodic memory deficit in Alzheimer's disease.